1. Field of the Invention
This invention relates to an optical communication device for bidirectionally sending control signals between a rotor-side circuit on the side of a rotary table and a stator-side circuit outside of the rotary table, including the circuit of a host computer, as well as a slip ring unit for an electronic component-mounting apparatus, for electrically and continuously connecting between a rotor-side circuit on the side of a rotary table and a stator-side circuit outside of the rotary table.
2. Prior Art
Conventionally, an optical communication device of this kind has been proposed e.g. by Japanese Laid-Open Patent Publication (Kokai) No. 8-83998, which is installed in a high-speed mounter. In the high-speed mounter, rotary table-side motor drivers on a rotor side and a host computer-side circuit on a stator side are connected to each other by an optical coupler formed by a pair of light-emitting/receiving elements, via which input/output (optical communication) of control signals is performed between the host computer and the motor drivers.
In the optical coupler, one of the light-emitting/receiving elements is secured on an end face of a shaft of the rotary table, and the other on an end face of a base, the two elements being opposed to each other on the rotation axis of the shaft.
As described above, in the conventional optical communication device, since the pair of light-emitting/receiving elements each serving as both a light-emitting element and alight-receiving element are used, each light-receiving element (light-receiving portion) is not capable of receiving light from an opposed light-emitting element (light-emitting portion) completely separately from light from an adjacent light-emitting element (light-emitting portion). To overcome this problem, the conventional optical device needs provision of a modulation circuit and a demodulation circuit, which results in an increase in manufacturing costs of the device.
In a high-speed mounter disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 6-37488, a plurality of slit disks and a plurality of photo-interrupters opposed to the slit disks are arranged on top of the shaft of a rotary table, to form detection means for sensing the positions of a plurality of mounting heads carried by the rotary table.
On the periphery of the rotary table, there are arranged mounting heads corresponding in number to the number of indexing steps for one turn of the rotary table, and further, around the periphery of the rotary table there are arranged a plurality of work stations including one for picking up an electronic component by vacuum and one for mounting the picked electronic component, in number dependent on the number of the indexing steps for one-turn of the rotary table, where face the mounting heads in temporary stoppage.
The above detection means detects which of the mounting heads that are assigned respective head numbers is positioned at which of the work stations, thereby enabling control of rotation and upward and downward motion of each of the mounting heads.
The mounting heads each carry a motor for rotating and lifting up and down itself, and supply of electrical drive power and input (or input/output) of a control signal are carried out via a slip ring mounted on the shaft of the rotary table. Therefore, in the conventional high-speed mounter, the slip and the above sensing means are arranged on the shaft of the rotary table separately from each other, and this not only requires a large installation space, but also increases the number of components and the steps of assembly process.
It is a first object of the invention to provide an optical communication device for permitting appropriate bidirectional optical communication between a stator-side circuit and a rotor-side circuit by ensuring separation of lights transmitted in opposite directions.
It is a second object of the invention to provide a slip ring unit which can attain the reduction of the number of components and space for installation of the components by unitizing a slip ring and rotation-sensing means of a rotary table.
To attain the first object, according to a first aspect of the invention, there is provided an optical communication device for communicating between a circuit arranged on a side of a stator and a circuit arranged on a side of a rotor having an axis of rotation.
The optical communication device according to the first aspect of the invention is characterized by comprising:
a pair of optical couplers arranged between the stator and the rotor, for permitting signals to be bidirectionally transmitted between the circuit arranged on the side of the stator and the circuit arranged on the side of the rotor,
one of the pair of optical couplers having a rotor-side light-receiving element arranged on the rotor such that the axis of rotation extends therethrough, and a stator-side light-emitting element arranged on the stator at a location away from the axis of rotation and having an optical axis directed toward the rotor-side light-receiving element, and
another of the pair of optical couplers having a stator-side light-receiving element arranged on the stator such that the axis of rotation extends therethrough, and a rotor-side light-emitting element arranged on the rotor at a location away from the axis of rotation and having an optical axis directed toward the stator- side light-receiving element.
According to this optical communication device, in one of the optical couplers, an optical signal emitted from the stator-side light-emitting element is received by the rotor-side light-receiving element, while in the other of the optical couplers, an optical signal emitted from the rotor-side light-emitting element is received by the stator-side light-receiving element.
The optical axis of the stator-side light-emitting element is directed toward the rotor-side light-receiving element on the axis of the rotor, and hence, even when the rotor-side light-receiving element rotates with rotation of the rotor, the optical signal from the stator-side light-emitting element does not miss the rotor-side light-emitting element and is positively received thereby. Similarly, the optical axis of the rotor-side light-emitting element is directed toward the stator-side light-receiving element on the axis of the rotor, and hence, even when the rotor-side light-emitting element rotates with rotation of the rotor, the optical signal from the rotor-side light-emitting element does not miss the stator-side light-receiving element and is positively received thereby.
Further, since the rotor-side light-emitting element is arranged at a location away from the axis of rotor, the rotor-side light-emitting element and the rotor-side light receiving element on the axis of the rotor do not interfere with each other by their locations. Similarly, since the stator-side light-emitting element is arranged at a location away from the axis of rotor, the stator-side light-emitting element and the stator-side light receiving element on the axis of the rotor do not interfere with each other by their locations.
Preferably, the stator-side light-emitting element and the stator-side light-receiving element are mounted on the stator in a state molded into one piece by using an optically transparent resin, and the rotor-side light-emitting element and the rotor-side light-receiving element are mounted on the rotor in a state molded into one piece by using an optically transparent resin.
Preferably, the stator-side light-emitting element and the rotor-side light-emitting element are each formed by a device selected from the group consisting of a light-emitting diode and a laser diode.
Preferably, the stator-side light-receiving element and the rotor-side light-receiving element are each formed by a device selected from the group consisting of a photo-transistor and a photo-diode.
To attain the first object, according to a second aspect of the invention, there is provided an optical communication device for communicating between a circuit arranged on a side of a stator and a circuit arranged on a side of a rotor having an axis of rotation.
The optical communication device according to the second aspect of the invention is characterized by comprising:
a pair of optical couplers arranged between the stator and the rotor, for permitting signals to be bidirectionally transmitted between the circuit arranged on the side of the stator and the circuit arranged on the side of the rotor,
one of the pair of optical couplers having a rotor-side light-receiving element arranged on the rotor such that the axis of rotation extends therethrough, a stator-side half-mirror arranged on the stator such that the axis of rotation extends therethrough, and a stator-side light-emitting element arranged on the stator and having an optical axis extending toward the rotor-side light-receiving element via the stator-side half-mirror, and
another of the pair of optical couplers having a stator-side light-receiving element arranged on the stator such that the axis of rotation extends therethrough, a rotor-side half-mirror arranged on the rotor such that the axis of rotation extends therethrough, and a rotor-side light-emitting element arranged on the rotor and having an optical axis extending toward the stator-side light-receiving element via the rotor-side half-mirror.
According to this optical communication device, in one optical coupler, the optical signal emitted from the stator-side light-emitting element is reflected from the stator-side half-mirror and then received by the rotor-side light-receiving element, while in the other optical coupler, the optical signal emitted from the rotor-side light-emitting element is reflected from the rotor-side half-mirror and received by the stator-side light-receiving element.
The optical axis of the stator-side light-emitting element is bent at the stator-side half-mirror and directed to the rotor-side light receiving element on the axis of the rotor, and hence even when the rotor-side light-receiving element rotates with rotation of the rotor, the optical signal from the stator-side light-emitting element does not miss the rotor-side light-emitting element and is positively received thereby. Similarly, the optical axis of the rotor-side light-emitting element is bent at the rotor-side half-mirror and directed to the stator-side light receiving element on the axis of the rotor, and hence, even when the rotor-side light-emitting element rotates with rotation of the rotor, the optical signal from the rotor-side light-emitting element does not miss the stator-side light-receiving element and is positively received thereby.
Further, since the rotor-side half-mirror enables the rotor-side light-emitting element to be arranged at a location away from the axis of rotor, the rotor-side light-emitting element and the rotor-side light-receiving element on the axis of the rotor do not interfere with each other by their locations. Similarly, since the stator-side half-mirror enables the stator-side light-emitting element to be arranged at a location away from the axis of rotor, the stator-side light-emitting element and the stator-side light receiving element on the axis of the rotor do not interfere with each other by their locations.
Preferably, the stator-side light-emitting element and the stator-side light-receiving element are mounted on the stator in a state molded into one piece by a first optically transparent resin, the stator-side half-mirror being formed on a phase boundary formed in the first optically transparent resin in a manner dividing the first optically transparent resin into two parts, and the rotor-side light-emitting element and the rotor-side light-receiving element are mounted on the rotor in a state molded in to one piece by a second optically transparent resin, the rotor-side half-mirror being formed on a phase boundary formed in the second optically transparent resin in a manner dividing the second optically transparent resin into two parts.
Preferably, the rotor-side half-mirror and the stator-side half-mirror are each formed on the phase boundary by depositing a metal coating thereon.
To attain the first object, according to a third aspect of the invention, there is provided an optical communication device for communicating between a circuit arranged on a side of a stator and a circuit arranged on a side of a rotor having an axis of rotation.
The optical communication device according to the third aspect of the invention is characterized by comprising:
a pair of optical couplers arranged between the stator and the rotor, for permitting signals to be bidirectionally transmitted between the circuit arranged on the side of the stator and the circuit arranged on the side of the rotor,
one of the pair of optical couplers having a light-emitting element arranged on one of the stator and the rotor such that the axis of rotation extends therethrough, and a light-receiving element arranged on another of the stator and the rotor such that the axis of rotation extends therethrough, and
another of the pair of optical couplers having an annular light-emitting element arranged on the another of the stator and the rotor in a manner concentric with respect to the axis of rotation, and an annular light-receiving element arranged on the one of the stator and the rotor in a manner concentric with respect to the axis of rotation.
According to this optical communication device, in one optical coupler, the optical signal emitted from the light-emitting element is received by the light-receiving element, while in the other optical coupler, the optical signal emitted from the annular light-emitting element is received by the annular light-receiving element.
The light-emitting element and the light-receiving element are arranged on the axis of the rotor, and hence even when any of these elements rotates with rotation of the rotor, the optical signal from the light-emitting element does not miss the light-emitting element and is positively received thereby. Similarly, the annular light-emitting element and the annular light-receiving element are concentrically arranged with respect to the axis of the rotor, and hence, even when any of these annular elements rotates with rotation of the rotor, the optical signal from the annular light-emitting element does not miss the annular light-receiving element and positively received thereby.
Further, since the light-emitting element and the annular light-receiving element can be are arranged such that they do not interfere with each other, and the light-receiving element and the annular light-emitting element can be arranged such that they do not interfere with each other.
Preferably, the annular light-emitting element comprises a first annular light-diffusing member, and a light-emitting diode arranged on a reverse side of the first annular light-diffusing member, and the annular light-receiving element comprises a second annular light-diffusing member, and a phototransistor arranged on a reverse side of the second annular light-diffusing member.
According to this preferred embodiment, even a light-emitting diode having a small light-emitting portion, and a phototransistor having a small light-receiving portion are used, an optical signal from the light-emitting diode can be positively received by the phototransistor. Further, it is preferred that a plurality of light-emitting diodes and a plurality of phototransistors are provided at equal intervals along the circumferences of the light-diffusing members associated therewith.
Preferably, the optical communication device includes an annular light shield arranged between the light-emitting element and the annular light-receiving element, and an annular light shield arranged between the light-receiving element and the annular light-emitting element.
According to this preferred embodiment, the light shields make it possible to prevent the optical signal emitted from the light-emitting element from being received by the annular light-receiving element adjacent thereto, and prevent the optical signal emitted from the annular light-emitting element from being received by the light-receiving element adjacent thereto.
To attain the second object, according to a fourth aspect of the invention, there is provided a slip ring unit for an electronic component-mounting apparatus including a rotary table carrying a plurality of mounting heads, a rotor-side circuit arranged in the rotary table, and a stator-side circuit arranged outside of the rotary table, the slip ring unit electrically connecting between the rotor-side circuit and the stator-side circuit.
The slip ring unit is characterized by comprising:
a slip ring, the slip ring having a rotary conductive member coaxially fixed on the rotary table and connected to the rotor-side circuit, and a brush member in sliding contact with the rotary conductive member and connected to the stator-side circuit;
a rotor coaxially fixed on the rotary conductive member;
an element arranged on the rotor for being sensed; and
a sensor opposed to the rotor for sensing the element arranged on the rotor.
According to this slip ring unit, in addition to the slip ring, the rotor having the member for being sensed, and the sensor are provided, and hence it is possible to detect the rotational angle of the rotary table or the positions of the mounting heads by way of the rotor. Further, since the rotation-sensing means and the slip ring are unitized, it is possible to reduce the number of components and space for installation of them. When a plurality of kinds of objects are detected in relation to the rotary table, it is preferred that there are provided a plurality of sets of rotors and sensors.
Preferably, the slip ring unit includes a housing covering the rotor and the sensor.
According to this preferred embodiment, the rotor and the sensor can be covered by the housing, whereby an erroneous detection caused by an environment, such as spilt lubricating oil and drifting dust, can be prevented.
Preferably, the slip ring unit further includes an optical coupler arranged coaxially with respect to the rotor, for permitting optical communication between the rotor-side circuit and the stator-side circuit, and supply of electrical drive power from the stator-side circuit to the rotor-side circuit is carried out via the brush member and the rotary conductive member, and transmission of signals from the stator-side circuit to the rotor-side circuit is carried out via the optical coupler.
According to this preferred embodiment, the slip ring can be made compact, and compared with the case of using a brush member, it is possible to enhance the reliability of input and output of control signals.
Preferably, the rotary conductive member includes a plurality of electrodes, and the brush member comprises a plurality of brush portions in sliding contact with the electrodes, respectively.
The above and other objects, features, and advantages of the invention will be made more apparent from the following detailed description taken in conjunction with the accompanying drawings.